-Hernández: concepción y diseño del estudio Todos los autores participaron en la recolección, análisis e interpretación de los datos, y en la redacción y revisión del manuscrito. Una serie de casos fatales de fiebre manchada de las Montañas Rocosas en Sonora, México Materials and methods:We conducted a cross-sectional study on a series of 47 deaths caused by Rickettsia rickettsii from 2013 to 2016. The diagnosis of Rocky Mountain spotted fever was confirmed in a single blood sample by polymerase chain reaction (PCR) or by a four-fold increase in immunoglobulin G measured in paired samples analyzed by indirect immunofluorescence. Clinical and laboratory characteristics were compared stratifying subjects into two groups: pediatric and adult.Results: There were no differences in clinical characteristics between groups; petechial rash was the most frequent sign (96%), followed by headache (70%) and myalgia (67%). Although that doxycycline was administered before the fifth day from the onset of symptoms, death occurred in 55% of patients. In clinical laboratory, thrombocytopenia, and biomarkers of liver acute failure and acute kidney failure were the most frequent. Conclusion: Rocky Mountain spotted fever remains as one of the most lethal infectious diseases, which may be related not only to the lack of diagnostic suspicion and delayed administration of doxycycline, 70Biomédica 2018;38:69-76 Delgado-De la Mora J, Licona-Enríquez JD, Leyva-Gastélum M, et al. but to genotypic characteristics of Rickettsia rickettsii that may play a role in the variability of the fatality rate that has been reported in other geographical regions where the disease is endemic.

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